Epithelial defenses are breached in many, suppurative airway diseases, such as primary ciliary dyskinesia and cystic fibrosis. Chronic, airway infection with bacteria stimulates an intense, inflammatory response that leads to progressive airway obstruction and bronchiectasis. Neutrophils migrate into the airway, and once there, release high concentrations of neutral serine proteases, like neutrophil elastase, during phagocytosis at the immediate epithelial surface. Neutrophil elastase and other proteases perpetuate the inflammatory response in the bronchiectatic airway by stimulating release of chemokines from the respiratory epithelium and interfering with bacterial clearance. Several strategies have been proposed to block the deleterious effects of proteases specifically in the airway, which have had limited success. We have developed a novel approach that permits the delivery of a potent antiprotease, alpha1-antitrypsin, to relatively inaccessible airways by targeting the respiratory epithelium via the polymeric immunoglobulin receptor, which concentrates the drug at the apical surface where it potentially could have the greatest impact on endobronchial infection and inflammation. In this proposal, we will test the hypothesis that airway-specific delivery of alpha1-antitrypsin more effectively blocks neutrophil-derived serine proteases at the immediate epithelial surface, thus enhancing clearance of bacteria and reducing the pulmonary inflammatory response in well-established cell and mouse models. We plan to characterize the bifunctional properties of anti-secretory component-human alpha1-antitrypsin in epithelial cell models and mice that specifically express the human polymeric immunoglobulin receptor in the airway. We will also determine whether transfected muscle can produce and secrete "targeted" human alpha1-antitrypsin to achieve a sustained, circulating level of the antiprotease. Finally, we will establish that protease inhibition affords greater protection against the damaging effects of the extracellular serine proteases, and reduce bacterial burden and prevent the escalation of the inflammatory response in murine models of Pseudomonas endobronchial infection. Using this approach, we will define the effects of neutrophil-derived serine proteases in the pathogenesis of airway inflammation and infection, and determine whether such "targeted" antiproteases could be used for therapeutic purposes in bronchiectasis and other airway diseases. [unreadable] [unreadable] [unreadable] [unreadable]